Diabetes is one of the major threats to human health in the 21st century. The number of patients is predicted to rise from 150-220 million in 2010 to 300 million in 2025. A majority of the patients have type II diabetes, which is characterized by insulin resistance. At present, therapy for type II diabetes relies mostly on reducing hyperglycaemia. It has limited efficacy and significant side effects. Thus, there is a need to develop more effective drugs for treating type II diabetes.
Evidence has shown that lipid accumulation in muscle and liver would lead to the development of insulin resistance. It has also been shown that reducing obesity or lowering lipids generally improves insulin sensitivity. Peroxisome proliferator-activated receptors (PPARs) belong to a family of nuclear receptors that regulate lipid metabolism. For example, PPARγ is highly expressed in adipocytes and mediates their differentiation. Thiazolidinediones (TZDs), a group of PPARγ agonists, have been demonstrated to be effective in treating type II diabetes. Studies suggest that TZDs may improve muscle insulin action and increase insulin sensitivity by sequestering lipids in adipocytes and reducing lipid accumulation in muscle.